The present invention relates to a continuous process for making an acyloxysilane mixture having up to about 40 percent by weight of alkoxyacyloxysilane, such as di-tertiarybutoxydiacetoxy silane. More particularly, the present invention relates to a method of initially feeding into a distillation column, a mixture of an alkyltrichlorosilane, such as methyltrichlorosilane, silicon tetrachloride, and an aliphatic carboxylic acid, such as acetic acid; concurrently, an alcohol, such as tertiary -butanol is separately introduced into the reboiler; a mixture of polyacyloxysilane and alkoxyacyloxysilane is continuously recovered from the reboiler in a separate receiving vessel. Acyloxy silanes are commonly used as cross-linking agents for one-part silicone RTV compositions. A procedure for making an acyloxysilane such as methyl triacetoxysilane is by reacting a chlorosilane such as methyltrichlorosilane with acetic anhydride. However, this procedure results in the formation of acetyl chloride which is a hazardous material.
Mixtures of acyloxysilane and alkoxyacyloxysilane also have been used as cross-linking agents for low modulus silicone RTV compositions, as shown by Lampe, U.S. Pat. No. 4,410,677. A continuous process for making alkoxysilanes and alkoxysiloxanes is shown by Schinabeck et al, U.S. Pat. No. 4,298,753. Methods for preparing acyloxysilanes by reacting chlorosilanes and aliphatic carboxylic acids are shown by John et al U.S. Pat. No. 4,176,130 and Petersen U.S. Pat. No. 4,329,484. Additional procedures for making mixtures of polyacyloxysilane and alkoxyacyloxysilane are therefor constantly being evaluated.